Biofilm growth can be stopped by injecting ‘cheater’ bacteria: IISc

Bangalore Mirror Bureau | Feb 28, 2016, 08.24 PM IST

By: Mihika Basu

​Biofilms form when bacteria cling to surfaces and are responsible for a host of diseases and infections. A biofilm can form on any surface exposed to bacteria and some amount of water. Now researchers from the Bengaluru-based Indian Institute of Science (IISc), have shown that formation of biofilms can be disrupted by “tweaking their social behaviour”.

The researchers said just like human communities, bacterial biofilms have their ‘shady’ characters, too. Widely called ‘cheaters’ and collectively called ‘cheater populations’, these bacteria refuse to partake in group behaviour that causes diseases, but still stay in the biofilm and reap the benefits. The IISc study, published in the journal Frontiers in Microbiology, shows infiltration of these non-cooperating cheaters can substantially weaken the biofilm, making it vulnerable to antibacterials and delay the origin and development of a disease.

The research focused on Salmonella entericaare, a class of bacteria that mainly cause of food-borne diseases worldwide. One of the main characteristics that makes this class of bacteria so virulent is their ability to form biofilms. Salmonella biofilms are known to occur on different surfaces including water distribution systems, food processing equipment, plant, and epithelial surfaces, while they also form persistent biofilms on gall stones in the host. Cells in a biofilm are notorious for their tolerance toward high doses of antimicrobials (for example, antibiotics), which is an agent that kills micro-organisms (include bacteria, fungi, archaea or protists and viruses) or inhibits their growth.

“Bacteria were traditionally believed to be free-living cells, but the perspective is fast changing with recognition of their social behavior. In this study, we evidently show that bacteria do cooperate in biofilms by producing public goods (matrix components). The cheaters do not contribute to the production of public good, but exploit the goods produced by the cooperators for their growth. The cheater infiltration caused a substantial reduction in the productivity of the overall biofilm and also reduced the strength of biofilm,” Prof Dipshikha Chakravortty, department of microbiology and cell biology, IISc, said.

The research team now plans to develop a ‘Trojan horse’ that could disrupt the biofilm.

FINDING’S SIGNIFICANCE

Biofilms provide strength to the bacteria against environmental stresses like the host immune system, antibiotics, heavy metals. They are a major burden in medicine. According to the researchers, biofilm is the predominant lifestyle of bacteria in their natural settings. They are collectives of bacterial cells enmeshed in an extracellular polymeric matrix. The matrix protects the biofilm bacteria from external stresses like antibiotics, apart from their other functions. “With this background, the key findings of our study was that matrix production is costly for the individual. However, infiltration of matrix-non-producer — that is the cheater — impairs the anti-microbial susceptibility of biofilm bacteria as well as delays its pathogenicity (origin and development of a disease). This implies that such infiltration makes the biofilm become susceptible to detergents and antibiotics,” said Prof Dipshikha Chakravortty, department of microbiology and cell biology, IISc.